/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
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 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
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 *    if and wherever such third-party acknowledgments normally appear.
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/**
 * BranchHandle is returned by specialized InstructionList.append() whenever a
 * BranchInstruction is appended. This is useful when the target of this
 * instruction is not known at time of creation and must be set later
 * via setTarget().
 *
 * @see InstructionHandle
 * @see Instruction
 * @see InstructionList
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 */
public final class BranchHandle extends InstructionHandle {
    private BranchInstruction bi; // An alias in fact, but saves lots of casts

    private BranchHandle(BranchInstruction i) {
        super(i);
        bi = i;
    }

    /** Factory methods.
     */
    private static BranchHandle bh_list = null; // List of reusable handles

    static final BranchHandle getBranchHandle(BranchInstruction i) {
        if (bh_list == null)
            return new BranchHandle(i);
        else {
            BranchHandle bh = bh_list;
            bh_list = (BranchHandle) bh.next;

            bh.setInstruction(i);

            return bh;
        }
    }

    /** Handle adds itself to the list of resuable handles.
     */
    protected void addHandle() {
        next = bh_list;
        bh_list = this;
    }

    /* Override InstructionHandle methods: delegate to branch instruction.
     * Through this overriding all access to the private i_position field should
     * be prevented.
     */
    public int getPosition() {
        return bi.position;
    }

    void setPosition(int pos) {
        i_position = bi.position = pos;
    }

    protected int updatePosition(int offset, int max_offset) {
        int x = bi.updatePosition(offset, max_offset);
        i_position = bi.position;
        return x;
    }

    /**
     * Pass new target to instruction.
     */
    public void setTarget(InstructionHandle ih) {
        bi.setTarget(ih);
    }

    /**
     * Update target of instruction.
     */
    public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
        bi.updateTarget(old_ih, new_ih);
    }

    /**
     * @return target of instruction.
     */
    public InstructionHandle getTarget() {
        return bi.getTarget();
    }

    /**
     * Set new contents. Old instruction is disposed and may not be used anymore.
     */
    public void setInstruction(Instruction i) {
        super.setInstruction(i);

        if (!(i instanceof BranchInstruction))
            throw new ClassGenException("Assigning " + i + " to branch handle which is not a branch instruction");

        bi = (BranchInstruction) i;
    }
}
